Variable valve timing system

ABSTRACT

A system for varying the valve timing of an internal combustion engine to increase the retarding effect of the engine for braking purposes, to increase the compression ratio of a relatively low compression ratio engine to enhance starting, and to optimize breathing to improve the engine performance over the useful operating speed range. The valve timing is varied by changing the total valve train length so as to shift the points on the cam profile at which the valve opening and closing events are determined.

United States Patent [1 1 Pelizzoni et al.

[ .Ian. 22, 1974 VARIABLE VALVE TIMING SYSTEM [75] Inventors: Winton J. Pelizzoni; Jack F.

. Greathouse; Frank J. Pekar, Jr.;

Richard B. Gibson, all of Hagerstown, Md.

[52] US. Cl. 123/97 B, 123/9016, 123/9017 [51] Int. Cl. F02d 13/04 [58] Field of Search 123/9016, 90.15, 97 B [56] References Cited UNITED STATES PATENTS 3,361,122 l/l968 Wagner 123/9016 3,304,925 2/1967 Rhoads 123/9016 3,385,274 5/1968 Shunta l23/90.l6 3,490,423 l/l970 Shunta 123/9016 3,641,988 2/1972 Torazza 123/9016 3,367,312 2/1968 Jonsson 123/9016 3,234,923 2/1966 Fleck 123/97' B 3,572,300 2/1969 Stager.... 123/97 B 3,426,523 2/1969 Straub 123/97 B SERVICE BRAKE FULL ON 5g; AIR T0 BRAKES AIR VALVE AIR FROM 3 nessnvom FUEL mazcnou PUMP BRAKE PEDAL SERVICE BRAKE START 3,547,087 12 1970 Siegler 123 97 B 3,439,661 4/1969 Weiler 123 97 B OTHER PUBLICATIONS Fuel Injection and Controls for Internal Combustion Engines, by Burman & DeLuca, 1962, pages 176177 Primary Examiner-Laurence M. Goodridge Assistant Examiner-Ronald B. Cox

Attorney, Agent, or Firm-Brumbaugh, Graves, Donohue & Raymond [57] ABSTRACT A system for varying the valve timing of an internal combustion engine to increase the retarding effect of the engine for braking purposes, to increase the compression ratio of a relatively low compression ratio engine to enhance starting, and to optimize breathing to improve the engine performance over the useful operating speed range. The valve timing is varied by changing the total valve train length so as to shift the points on the cam profile at which the valve opening and closing events are determined.

36 Claims, 36 Drawing Figures FATENTED JAN 2 2 I974 3.786.792 SHEET 010F 21 MOTORING COMPRESSION AND EXPANSION uJ O: 3 (0 LL] Lt 3! INTAKE VOLUME l l I x3 MOTORING F/G Ir ENG'INE BRAKING EXHAUST VALVE OPENED COMPRESSION I; EXPANSION INTO THE g EXHAUST MANIFOLD M E 0: CL,

INTAKE INVENTORS. VOLUME WINTON J. PELIZZONI,

JACK F. GREATHOUSE, BY FRANK J. PEKAR,JR. BI

RICHARD B. GIBSON I h e I r A TTORNEYS.

PATENTED AIIZB m4 3. 786, 792 SHEET 02 [If 21 CYLINDER PRESSURE I EXHAUST VALVE; 3'9

I ENGINE BRAKE ON I E INLET T VALVE .3 LLI I EXHAUST VALVE -ENGINE\\ BRAKE OFF I I I I I l I I I I I I INTAKE COMPRESSION POWER EXHAUST INVENTORS. WINTON' J. PELIZZONI, JACK F. 'GREATHOUSE, BY FRANK J. PEKAR'JRBI RICHARD a. GIBSON SCHEMATIC OE 4 STROKE CYCLE EVENTS WITH COMPRESSION BRAKING VALVE ACTION PATENTEDJAN 22 m4 SHEEI UH 0F 21 CAB SWITCH SERVICE BRAKE START SERVICE BRAKE FULL em AIR TO BRAKES AIR VALVE RESERVOIR INVENTORS. I WINTON J. mauzzom JACK F. GREATHOUSE,

y FRANK .1. PEKAR, JR. 8 RICHARD B. meson A from/5Y5.

PATENTEUJAN 22 m4 HORSEPOWER mm user 211 BRAKE 8 FR/GT/O/V HORSEPOWER v BRAKE HORSEPOWER TORQUE LBS TWO CYL. HEADS (4 CYLS.) OPERATING THREE CYL. HEADS (6 CYLS.) I26 ENGINE BRAKE (FULL) (8 CYLS.)

I i I l 1 ENGINE FRICTION I000 I200 I400 I600 I800 2000 2200 2400 2600 ENGINE RPM WINTON JACK F. GREATHOUSE BY FRANK .1.

RICHARD A r TOR/VE rs.

their I N VEN TORS.

J PELIZ 2 ON I,

PE KAR, JR. 5. GIBSON snzit PATENTEHmzz m4 PATENTEDJAfi 2 2 1974 mm mar 21 I NVEN TORS WINTON J. PELIZZONI, JACK F. GREATHOUSE BY FRANK J. PEKAR, JR. 8|

RICHARD B. GIBSON 'bcmur 49 4" inr u r ymnl their ATTORNEYS.

PATENTEU JAN 2 2 I974 I 3.786.792 sIIEIII osur 2'I i CAB SWITCH I INJECTION BATTERY r PUMP U SWITCH ENGINE I00 BRAKE ON '86 I T 37 sERvICE BRAKE sTART%:: SOLENOIDSI SERVICE BRAKE FULL ON 85' as F/G. HA

C B SWITCH 37 NJECTIoN BATTERY 4r PUMP SOLENOIDS V SWITCH 85 I I00 L 38 F l6. //5

I04 SHIFT LEVER I02 87 CAB SWITCH wn- I INJECTIoN I I BATTERY PUMP SOLENOIDS SWITCH CAB SWITCH W E 87 A INJECTION- I BATTERY -1 PUMP SOLENOIDS V V SWITCH I00 264 i J85 88 F/G. l/D INVENTORS. WINTON J. PELIZZONI, JACK F. GREATHOUSE, Y FRAN J. PEKAR, JR.&

RICH D B. GIBSON. BM 4&-,M*

their ATTORNEYS.

PATENTEDJMIZZISN 3,786,792

' sum 10 P T1 I04 BRAKE PEDAL 272 94 SERVICE BRAKE 50 I48 274 START SERVICE BRAKE II FULL ON -k AIR TO BRAKES fi 5 "Ki- 3 L 72 CAB SWITCH V I n 11" A I "A H 78 I v I02 ELISE ,F--\. r v

' ma I 6 l I M:

1 W. 58 "*60 l ill T 59 l/ 42 I I A K A! 56\ 161- F/GJ I INVENTORS. WINTON J. PELIZZONI JACK F. GREATHOUSE,

BY FRANK J. PEKAR, JR. 8-

RICHARD B. GIBSON BQUMJM M vW their ATTORNEYS.

Pmmmmzelw 3.786.792 mm 1m 2w 7 INVENTO WINT J. PELIZZ I,

JACK GREATHOUSE, BY FRANK J. PEKAR, JR.&

RICHARD B. GIBSON their ATTORNEYS.

PATENIEW 9 3, 7 86, 7' 9 2 sum no; 21

CYLINDER E 1 gi PRESSURE 5:; 3L- E COMPRESSIQN EXPANSION INLET VALVE CLEARANCE 7 0 SET TO PERMIT CLOSING NORMAL INLET VALVE AT BOTTOM CENTER CLEARANCE CLEARANCE VOLUME CLEARANCE VOLUME m9 340 mfg 2 M 55 1 2 {Zen E u 2 0w 3 E m .1 o mu. m? 2 3 ""339 3 I MI ass/I POSITION OF CRANK, CONNECTING ROD POSITION OF CRANK, CONNECTING ROD AND PIETON WHEN INLET VALVE CLOSES AND PISTON WHEN INLET VALVE NOFIMALLY CLOSES AT BOTTOM CENTER INVENTORS. j V F/ WINTON J. PELIZZONI, JACK F. GREATHOUSE,

BY FRANK J. PEKAR, JR. & RICHARD B. GIBSON Iheir ATTORNEYS.

PMEMED M 2 I 7 3 7' 86 f 9 2 sum. 1M! 21 CAB SWITCH THROTTLE LIMITING SOLENOID 76 /85 FUEL 82 INJECTION 383: 373

- m 55 l T 5 q 6 I I62 =i=-*.E

w i INVENTORS, WINTQN J. PELIZZONI,

JACK F. GREATHOUSE, FRANK J. PEKAR, JR. 5

RICHARD B. GIBSON.

their ATTORNEYS.

PATENIEBJAH 22 1974 MN 15 0F 2? I N VENTORS WINTON J. PELIZZONI, JACK F. GREATHOUSE, BY FRANK J. PEKAR, JR. a

RICHARD GIBSON their ATTORNEYS.

BRAKE PEDAL I02 SWITCHES CAB SWITCH INJECTION PUMP SWITCH I -l0fl BATTERY CAB SWITCH THROTTLE LIMITING SOLENOID GINE a VARYING BRAKING COMPRESSION RATIO 3 E LOW SPEED +IIGI-I SPEED g VALVE TIMING I VALVE TIMING I I RPM SPEED AT WHICH p VALVE TIMING INVbNIORS- SHIFTED I wINToN II. PELIZZONI,

JACK F. GREATHOUSE, BY FRANK J. PEKAR, JR. HI RICHARD B. GIBSON their ATTORNEYS.

PATENTEDJANZZ m4 3,786, 7 9 2 MN 17% m EXHAUST 76 INLET ROCKER ARM ROCKER ARM I j If I q AK A 190 34 g]: ist-' m 420 407 11 OTL 405 UNDER 76. IPRESSURE 2 i p M- 1 BRAKE swfigfiis 93 IUZ INJECTION PUMP SWITCH CAB SW'TCH WINTON A THROTTLE BY l m J 1%;??? a BATTERY A LIMITING RICHARD a. GIBSON I V SOLENOID 4 385 392 their ATTORNEYS. 

1. A variable valve timing system for an internal combustion engine having a crankshaft and at least one cylinder, a piston reciprocable in each cylinder and connected to the crankshaft for rotation thereof, and at least one valve for each cylinder, comprising at least one cam means driven by the crankshaft, the cam means including a first profile for actuating a corresponding valve in a first timed relation to the rotation of the crankshaft and a second profile for actuating at least one of the valves in a second timed relation to the rotation of the crankshaft, the cam means for actuating any valve in two timed relations to the rotation of the crankshaft including a cam having the first and second profiles formed thereon circumferentially spaced from each other, a valve gear train coupling each valve to a corresponding one of the cam means, means for expanding at least one of the valve gear trains from a collapsed condition in which the first profile is effective for actuating the corresponding valve in the first timed relation to the rotation of the crankshaft to an expanded condition in which the second profile is effective for actuating the corresponding valve in the second timed relation to the rotation of the crankshaft, each valve capable of being actuated in the two timed relations to the rotation of the crankshaft being coupled to the first and second profiles of the corresponding cam by a single valve gear train, and means for locking each expanded valve gear train in the expanded condition, whereby each valve actuated by an expandable valve gear train is actuated in one of two predetermined timed relations to the rotations of the crankshaft corresponding to the collapsed and the locked expanded conditions of the corresponding valve gear train, each expanding means including means forming a hydraulic chamber having an inlet port, a piston reciprocally disposed in the chamber, and means for supplying pressurized hydraulic fluid through the inlet port into the chamber, and the locking means including check valve means for trapping the pressurized hydraulic fluid in the chamber and preventing the trapped fluid from exiting the chamber, and means for biasing the check valve means to seal the chamber to prevEnt hydraulic fluid in the chamber from exiting therefrom.
 2. A variable valve timing system for an internal combustion engine having a crankshaft and at least one cylinder, a piston reciprocable in each cylinder and connected to the crankshaft for rotation thereof, and at least one valve for each cylinder, comprising at least one cam means driven by the crankshaft, the cam means including a first profile for actuating a corresponding valve in a first timed relation to the rotation of the crankshaft and a second profile for actuating at least one of the valves in a second timed relation to the rotation of the crankshaft, the cam means for actuating any valve in two timed relations to the rotation of the crankshaft including a cam having the first and second profiles formed thereon circumferentially spaced from each other, a valve gear train coupling each valve to a corresponding one of the cam means, means for expanding at least one of the valve gear from a collapsed condition in which the first profile is effective for actuating the corresponding valve in the first timed relation to the rotation of the crankshaft to an expanded condition in which the second profile is effective for actuating the corresponding valve in the second timed relation to the rotation of the crankshaft, each valve capable of being actuated in the two timed relations to the rotation of the crankshaft being coupled to the first and second profiles of the corresponding cam by a single valve gear train, each expanding means including means forming a hydraulic chamber having an inlet port, a piston reciprocally disposed in the chamber, and means for supplying pressurized hydraulic fluid through the inlet port into the chamber, means for locking each expanded valve gear train in the expanded condition, whereby each valve actuated by an expandable valve gear train is actuated in one of two predetermined timed relations to the rotation of the crankshaft corresponding to the collapsed and the locked expanded conditions of the corresponding valve gear train, the locking means including check valve means for trapping the pressurized hydraulic fluid in the chamber and preventing the trapped fluid from exiting the chamber through the inlet port, and means for biasing the check valve means to seal the inlet port to prevent the hydraulic fluid from exiting therethrough, and also including means for biasing the piston in the direction to expand the associated valve gear train, and control means for selectively disabling the check valve means and preventing the hydraulic fluid from being trapped in the chamber, whereby when the check valve means is disabled, the piston is able to reciprocate in the chamber, the corresponding second profile is rendered ineffective, and the corresponding valve is actuated in the first timed relation to the rotation of the crankshaft.
 3. A variable valve timing system for an internal combustion engine having a crankshaft and at least one cylinder, a piston reciprocable in each cylinder and connected to the crankshaft for rotation thereof, and at least one valve for each cylinder, comprising at least one cam means driven by the crankshaft, the cam means including a first profile for actuating a corresponding valve in a first timed relation to the rotation of the crankshaft and a second profile for actuating at least one of the valves in a second timed relation to the rotation of the crankshaft, a valve gear train coupling each valve to a corresponding one of the cam means, means for expanding at least one of the valve gear trains to render the second profile effective for actuating the corresponding valve in the second timed relation to the rotation of the crankshaft, each expanding means including means forming a hydraulic chamber having an inlet port, a piston reciprocally disposed in the chamber, and means for supplying pressurized hydraulic fluid through the inlet port into the chamber, means for locking each expanded valve gear train in an expanded condition, the locking meanS including check valve means for trapping the pressurized hydraulic fluid in the chamber and preventing the trapped fluid from exiting the chamber through the inlet port, means for biasing the piston in the direction to expand the associated valve gear train, means for biasing the check valve means to seal the inlet port to prevent the hydraulic fluid from exiting therethrough, and control means for selectively disabling the check valve means and preventing the hydraulic fluid from being trapped in the chamber, whereby when the check valve means is disabled, the piston is able to reciprocate in the chamber, the corresponding second profile is rendered ineffective, and the corresponding valve is actuated in the first timed relation to the rotation of the crankshaft, the control means including means forming a control chamber, a control piston reciprocally disposed in the control chamber, the control piston including a finger adapted to displace the check valve means into spaced non-sealing relation to the inlet port to permit hydraulic fluid to exit therethrough, means for biasing the control piston to displace the check valve means, and means for supplying pressurized hydraulic fluid to the portion of the control chamber intermediate the control piston and the check valve means to develop a force which urges the control piston away from the check valve means.
 4. The system according to claim 3, wherein the cam means for actuating any valve in two timed relations to the rotation of the crankshaft includes a cam having the first and second profiles formed thereon circumferentially spaced from each other.
 5. The system according to claim 3, wherein the control means also includes means for supplying hydraulic fluid to the portion of the control chamber on the side of the control piston remote from the check valve means, and means for selectively shifting the pressure of the hydraulic fluid in the remote control chamber portion between substantially atmospheric pressure and substantially the same pressure as that of the pressurized hydraulic fluid in the control chamber portion between the control piston and check valve means.
 6. The system according to claim 1, wherein each hydraulic chamber forming means and each corresponding piston comprise a portion of the corresponding valve gear train coupling the corresponding valve with the second cam profiles.
 7. The system according to claim 6, wherein each hydraulic chamber forming means and each corresponding piston are mounted for reciprocation in the block of the internal combustion engine.
 8. The system according to claim 6, wherein the valve gear trains include rocker arms coupling the valves to at least some of the cam means, and each hydraulic chamber forming means and each corresponding piston are mounted in the rocker arm which actuates the corresponding valve in the first and second timed relations to the rotation of the crankshaft.
 9. The system according to claim 8, including at least one rocker arm shaft for mounting the rocker arms for rocking motion, each rocker arm shaft mounting a rocker arm coupled to a valve whose timing may be varied being formed with two passageways, the first passageway being adapted to be communicated with a source of pressurized hydraulic fluid for supplying pressurized hydraulic fluid for lubricating each rocker arm carried by the rocker arm shaft, and the second passageway being adapted to be communicated with the expanding means, control valve means mounted in each rocker arm shaft formed with the two passageways for selectively communicating the second passageway with the first passageway, and for selectively sealing the second passageway from the first passageway and exposing the hydraulic fluid in the second passageway to atmospheric pressure, and means for actuating the control valve means to expand the valve gear trains of the valves whose timing is to be varied.
 10. A variable valve timing system for an internal combustion engine having a crankshafT and at least one cylinder, a piston reciprocable in each cylinder and connected to the crankshaft for rotation thereof, and at least one valve for each cylinder, comprising at least one cam means driven by the crankshaft, the cam means including a first profile for actuating a corresponding valve in a first timed relation to the rotation of the crankshaft and a second profile for actuating at least one of the valves in a second timed relation to the rotation of the crankshaft, a valve gear train coupling each valve to a corresponding one of the cam means, each valve gear train including a rocker arm coupling the valve to a corresponding cam means, means for expanding at least one of the valve gear trains to render the second profile effective for actuating the corresponding valve in the second timed relation to the rotation of the crankshaft, each expanding means including means forming a hydraulic chamber having an inlet port, a piston reciprocally disposed in the chamber, and means for supplying pressurized hydraulic fluid through the inlet port into the chamber, means for locking each expanded valve gear train in an expanded condition, the locking means including check valve means for trapping the pressurized hydraulic fluid in the chamber and preventing the trapped fluid from exiting the chamber through the inlet port, each hydraulic chamber forming means and each corresponding piston comprising a portion of the corresponding valve gear train coupling the corresponding valve with the second cam profile and being mounted in the rocker arm which actuates the corresponding valve in the first and second timed relations to the rotation of the crankshaft, at least one rocker arm shaft for mounting the rocker arm for rocking motion, each rocker arm shaft mounting a rocker arm coupled to a valve whose timing may be varied being formed with two passageways, the first passageway being adapted to be communicated with a source of pressurized hydraulic fluid for supplying pressurized hydraulic fluid for lubricating each rocker arm carried by the rocker arm shaft, and the second passageway being adapted to be communicated with the expanding means, control valve means mounted in each rocker arm shaft formed with the two passageways for selectively communicating the second passageway with the first passageway, and for selectively sealing the second passageway from the first passageway and exposing the hydraulic fluid in the second passageway to atmospheric pressure, means for actuating the control valve means to expand the valve gear train of each valve whose timing is to be varied, means forming a control chamber mounted in each rocker arm coupled to a valve whose timing is to be varied, a control piston reciprocally disposed in the control chamber, the control piston including a finger adapted to displace the check valve means into spaced non-sealing relation to the inlet port to permit hydraulic fluid to exit therethrough, means for biasing the control piston to displace the check valve means, a first conduit communicating the portion of the control chamber intermediate the control piston and the check valve means with the first passageway in the rocker arm shaft, and a second conduit communicating the portion of the control chamber on the side of the control piston remote from the check valve means with the second passageway in the rocker arm shaft.
 11. The system according to claim 10, including means for biasing the piston in the hydraulic chamber to expand the associated valve gear train, and means for biasing the check valve means to seal the inlet port of the hydraulic chamber.
 12. A variable valve timing system for an internal combustion engine having a crankshaft and at least one cylinder, a piston reciprocable in each cylinder and connected to the crankshaft for rotation thereof, and at least one inlet valve and at least one exhaust valve for each cylinder, comprising a plurality of cam means driven by the crankshaft, the cam means including first profiles for actuatIng the valves in a first timed relation to the rotation of the crankshaft and second profiles for actuating at least one of the valves in a second timed relation to the rotation of the crankshaft, a plurality of valve gear trains coupling the inlet and exhaust valves to corresponding ones of the cam means, means for expanding at least one of the valve gear trains from a collapsed condition in which the first profiles are effective for actuating the corresponding valves in the first timed relation to the rotation of the crankshaft to an expanded condition in which the second profiles are effective for actuating the corresponding valves in the second timed relation to the rotation of the crankshaft, and means for locking the expanded valve gear trains in the expanded condition, whereby the valves actuated by the expandable valve gear trains are actuated in one of two predetermined timed relations to the rotation of the crankshaft corresponding to the collapsed and the locked expanded conditions of the corresponding valve gear trains, each expanding means including means forming a hydraulic chamber having an inlet port, a piston reciprocally disposed in the chamber, and means for supplying pressurized hydraulic fluid through the inlet port into the chamber, and wherein the locking means includes check valve means for trapping the pressurized hydraulic fluid in the chamber and preventing the trapped fluid from exiting the chamber through the inlet port, each hydraulic chamber forming means and each corresponding piston comprising a portion of the corresponding valve gear train coupling the corresponding valve with the second cam profiles, the valve gear trains including rocker arms coupling the valves to at least some of the cam means, and each hydraulic chamber forming means and each corresponding piston being mounted in the rocker arm which actuates the corresponding valve in the first and second timed relations to the rotation of the crankshaft, including at least one rocker arm shaft for mounting the rocker arms for rocking motion, each rocker arm shaft mounting a rocker arm coupled to a valve whose timing may be varied being formed with two passageways, the first passageway being adapted to be communicated with a source of pressurized hydraulic fluid for supplying pressurized hydraulic fluid for lubricating each rocker arm carried by the rocker arm shaft, and the second passageway being adapted to be communicated with the expanding means, control valve means mounted in each rocker arm shaft formed with the two passageways for selectively communicating the second passageway with the first passageway, and for selectively sealing the second passageway from the first passageway and exposing the hydraulic fluid in the second passageway to atmospheric pressure, and means for actuating the control valve means to expand the valve gear trains of the valves whose timing is to be varied, each rocker arm shaft mounting a plurality of rocker arms coupled to valves whose timing may be varied being formed with a third passageway adapted to be communicated with some of the expanding means, the second passageway being adapted to be communicated with the other expanding means, and including additional control valve means for selectively communicating the third passageway with the first passageway, and for selectively sealing the third passageway from the first passageway and exposing the hydraulic fluid in the third passageway to atmospheric pressure, and means for actuating the additional control valve means to expand the corresponding valve gear trains independently of the expansion of the valve gear trains associated with the second passageway, whereby the timing of some of the valves may be shifted to one timed relation to the rotation of the crankshaft upon expansion of the associated valve gear trains, and the timing of other valves may be shifted to a different timed relation upon expansion of the associated valve gear trains.
 13. The system according to claim 1, wherein each first cam pRofile is disposed with respect to the position of the crankshaft such that the corresponding valve is opened and closed at optimum times for enhancing engine performance in the lower engine operating speed range, and each second cam profile is disposed with respect to the position of the crankshaft such that the corresponding valve is opened and closed at optimum times for enhancing engine performance in the upper engine operating speed range, and including engine speed responsive means for controlling the means for expanding the valve gear train to render each second cam profile effective.
 14. The system according to claim 1, wherein there is at least one inlet valve for each cylinder and at least one inlet valve may be actuated in response to the first and second cam profiles, each second cam profile being disposed with respect to the position of the crankshaft such that the corresponding inlet valve is closed in response thereto during the initial portion of the compression stroke, and each first cam profile being disposed with respect to the position of the crankshaft such that the corresponding inlet valve is closed in response thereto when the corresponding piston is closer to the bottom dead center position, so that the effective compression ratio is higher when the timing of the corresponding inlet valve is determined by the first cam profile than when the timing is determined by the second cam profile, and including means for actuating the means for expanding the valve gear train to render each second cam profile effective and for collapsing the valve grear train to render the first cam profile effective.
 15. The system according to claim 14, including means for limiting the maximum engine speed when the valve gear train is collapsed to render the first cam profile effective, the engine speed limiting means being coupled to the means for actuating the valve gear train expanding means so that the maximum engine speed limiting means is automatically activated when the valve gear train is collapsed.
 16. The system according to claim 15, wherein the internal combustion engine is supplied with fuel by a fuel injection system including an engine speed governor and a control element which may be positioned for a desired governed engine speed, and wherein the maximum engine speed limiting means includes a displaceable stop member for limiting the travel of the control element.
 17. The system according to claim 1, wherein there is at least one exhaust valve for each cylinder and at least one exhaust valve may be actuated in response to the first and second cam profiles, each second cam profile being disposed with respect to the position of the crankshaft such that the corresponding exhaust valve is opened in response thereto at or near the end of the compression stroke to dump the compressed air in the corresponding cylinder so as to increase the retarding effect of the engine, and including means for actuating the means for expanding the valve gear train to render each second cam profile effective and for collapsing the valve gear train to render the first cam profile effective.
 18. A variable valve timing system for an internal combustion engine having a crankshaft and at least one cylinder, a piston reciprocable in each cylinder and connected to the crankshaft for rotation thereof, and at least one valve for each cylinder, comprising at least one cam means driven by the crankshaft, the cam means including a first profile for actuating a corresponding valve in a first relation to the rotation of the crankshaft and a second profile for actuating at least one of the valves in a second timed relation to the rotation of the crankshaft, the cam means for actuating any valve in two timed relations to the rotation of the crankshaft including a cam having the first and second profiles formed thereon circumferentially spaced from each other, a valve gear train coupling each valve to a corresponding one of the cam means, means for expanding at least one of the valve Gear trains from a collapsed condition in which the first profile is effective for actuating the corresponding valve in the first timed relation to the rotation of the crankshaft to an expanded condition in which the second profile is effective for actuating the corresponding valve in the second timed relation to the rotation of the crankshaft, each valve capable of being actuated in the two timed relations to the rotation of the crankshaft being coupled to the first and second profiles of the corresponding cam by a single valve gear train, and means for locking each expanded valve gear train in the expanded condition, whereby each valve actuated by an expandable valve gear train is actuated in one of two predetermined timed relations to the rotation of the crankshaft corresponding to the collapsed and the locked expanded conditions of the corresponding valve gear train, at least one exhaust valve capable of being actuated in response to the first and second cam profiles, each second cam profile being disposed with respect to the position of the crankshaft such that the corresponding exhaust valve is opened in response thereto at or near the end of the compression stroke to dump the compressed air in the corresponding cylinder so as to increase the retarding effective of the engine, and including means for actuating the means for expanding the valve gear train to render each second cam profile effective and for collapsing the valve gear train to render the first cam profile effective, the internal combustion engine including fuel supply means for delivering fuel to the cylinders, and including means for sensing the fuel delivery to the cylinders, and means responsive to the fuel delivery sensing means for disabling the means for actuating the valve gear train expanding means while fuel is delivered to the cylinders.
 19. The system according to claim 18, wherein the fuel supply means includes a movable member for controlling the fuel delivery to the cylinders, and the means for actuating the valve gear train expanding means is responsive to motive force, and including a source of motive force, means for communicating the actuating means with the source of motive force, and wherein the fuel delivery sensing means and the disabling means include switch means in the communicating means operable to selectively effect and terminate communication between the source of motive force and the actuating means, and means coupling the switch means with the movable member.
 20. The system according to claim 19, wherein the fuel supply means includes a fuel injection pump having a control rack, and wherein the switch means is mounted in operative relation to the control rack, whereby the switch means is actuated by the control rack to collapse the valve gear trains to render the first cam profiles effective before fuel is delivered to the cylinders.
 21. The system according to claim 20, wherein the fuel supply means includes an engine speed responsive governor coupled to the control rack, whereby the governor prevents stalling of the engine by positioning the control rack to actuate the switch means and disable the actuating means and to deliver fuel to the cylinders.
 22. The system according to claim 19, wherein the internal combustion engine is mounted in a vehicle having braking means, and a brake pedal for activating the brake means, and including switch means mounted in operative relation to the brake pedal and connected in the communicating means in series with the source of motive force, the disabling switch means and the actuating means, whereby the valve gear trains may be expanded when the brake pedal is depressed to activate the brake pedal switch means and there is no fuel delivery to the cylinders.
 23. A variable valve timing system for an internal combustion engine having a crankshaft and at least one cylinder, a piston reciprocable in each cylinder and connected to the crankshaft for rotation thereof, at least one exhaust valve for each cylinder, and meanS for supplying fuel to each cylinder, comprising means forming a first cam profile for actuating each exhaust valve in a first timed relation to the rotation of the crankshaft for normal operation of the engine, means forming a second cam profile for opening at least one exhaust valve at or near the end of the compression stroke to dump the compressed air from each corresponding cylinder so as to increase the retarding effect of the engine, means for selectively coupling the second cam profile means with each corresponding exhaust valve, means for sensing the fuel delivery to the cylinders, and means responsive to the fuel delivery sensing means for disabling the coupling means and thereby rendering the second cam profile means ineffective while fuel is delivered to the cylinders.
 24. Apparatus for varying the timing of at least one of the valves of an internal combustion engine having a crankshaft and at least one cylinder associated with the valves, a piston reciprocable in each cylinder and connected to the crankshaft for rotation thereof, first cam means for actuating the valves in a first timed relation to the rotation of the crankshaft, second cam means for actuating at least some of the valves in a second timed relation to the rotation of the crankshaft, and a plurality of valve gear trains coupling the valves to the corresponding first and second cam means, comprising means forming a hydraulic chamber having an inlet port and adapted to receive pressurized fluid through the inlet port, a piston reciprocally disposed in the chamber, the hydraulic chamber forming means and the piston being a portion of each valve gear train coupling a valve with the corresponding second cam means, check valve means for trapping the pressurized hydraulic fluid in the chamber and preventing the trapped fluid from exiting the chamber, and means for biasing the check valve means to seal the chamber to prevent hydraulic fluid in the chamber from exiting therefrom.
 25. Apparatus for varying the timing of at least one of the valves of an internal combustion engine having a crankshaft and at least one cylinder associated with the valves, a piston reciprocable in each cylinder and connected to the crankshaft for rotation thereof, first cam means for actuating the valves in a first timed relation to the rotation of the crankshaft, second cam means for actuating at least some of the valves in a second timed relation to the rotation of the crankshaft, and a plurality of valve gear trains coupling the valves to the corresponding first and second cam means, comprising means forming a hydraulic chamber having an inlet port and adapted to receive pressurized fluid through the inlet port, a piston reciprocally disposed in the chamber, the hydraulic chamber forming means and the piston being a portion of each valve gear train coupling a valve with the corresponding second cam means, check valve means for trapping the pressurized hydraulic fluid in the chamber and preventing the trapped fluid from exiting the chamber through the inlet port, means for biasing the piston in the direction to expand the volume of the hydraulic chamber, means for biasing the check valve means to seal the inlet port to prevent hydraulic fluid in the chamber from exiting therethrough, and control means for selectively disabling the check valve means and preventing hydraulic fluid in the chamber from being trapped therein, whereby when the check valve means is disabled, the piston is able to reciprocate in the chamber, the corresponding second cam means are rendered ineffective, and the corresponding valve is actuated in the first timed relation to the rotation of the crankshaft.
 26. Apparatus for varying the timing of at least one of the valves of an internal combustion engine having a crankshaft and at least one cylinder associated with the valves, a piston reciprocable in each cylinder and connected to the crankshaft for rotation thereof, first cam means for actuating the valves in a first timed relation to the rotaTion of the crankshaft, second cam means for actuating at least one of the valves in a second timed relation to the rotation of the crankshaft, and a plurality of valve gear trains coupling the valves to the corresponding first and second cam means, comprising means forming a hydraulic chamber having an inlet port and adapted to receive pressurized fluid through the inlet port, a piston reciprocally disposed in the chamber, the hydraulic chamber forming means and the piston being a portion of each valve gear train coupling a valve with the corresponding second cam means, check valve means for trapping the pressurized hydraulic fluid in the chamber and preventing the trapped fluid from exiting the chamber through the inlet port, means for biasing the piston in the direction to expand the volume of the hydraulic chamber, means for biasing the check valve means to seal the inlet port to prevent hydraulic fluid in the chamber from exiting therethrough, and control means for selectively disabling the check valve means and preventing hydraulic fluid in the chamber from being trapped therein, whereby when the check valve means is disabled, the piston is able to reciprocate in the chamber, the corresponding second cam means are rendered ineffective, and the corresponding valve is actuated in the first timed relation to the rotation of the crankshaft, the control means including means forming a control chamber, a control piston reciprocally disposed in the control chamber, the control piston including a finger adapted to displace the check valve means into spaced non-sealing relation to the inlet port to permit hydraulic fluid to exit therethrough, and means for biasing the control piston to displace the check valve means.
 27. Apparatus according to claim 26, including means forming a first port communicating with the portion of the control chamber intermediate the control piston and the check valve means adapted to admit pressurized hydraulic fluid thereto, and means forming a second port communicating with the portion of the control chamber on the side of the control piston remote from the check valve means adapted to admit pressurized hydraulic fluid thereto.
 28. The system according to claim 3, wherein the hydraulic chamber forming means and the corresponding piston of each expanding means are mounted for reciprocation in the block of the internal combustion engine.
 29. The system according to claim 3, wherein the valve gear trains include rocker arms coupling the valves to at least some of the cam means, and the hydraulic chamber forming means and the corresponding piston of each expanding means are mounted externally of the rocker arm which actuates the corresponding valve in the first and second timed relations to the rotation of the crankshaft.
 30. The system according to claim 3, wherein the valve gear train includes rocker arms coupling the valves to at least some of the cam means, and the hydraulic chamber forming means and the corresponding piston of each expanding means are mounted in the rocker arm which actuates the corresponding valve in the first and second timed relations to the rotation of the crankshaft.
 31. The system according to claim 10, wherein the cam means for actuating any valve in two timed relations to the rotation of the crankshaft includes a cam having the first and second profiles formed thereon circumferentially spaced from each other.
 32. The apparatus according to claim 26, wherein the hydraulic chamber forming means and the corresponding piston of each valve gear train coupling a valve with the corresponding second cam means are mounted for reciprocation in the block of the internal combustion engine.
 33. The apparatus according to claim 26, wherein the valve gear trains include rocker arms coupling the valves to at least some of the cam means, and the hydraulic chamber forming means and the corresponding piston of each valve gear train coupling a valve with the corresponding second cam means are mounted externally of tHe rocker arm which actuates the corresponding valve in the first and second timed relations to the rotation of the crankshaft.
 34. The apparatus according to claim 26, wherein the valve gear trains include rocker arms coupling the valves to at least some of the cam means, and the hydraulic chamber forming means and the corresponding piston of each valve gear train coupling a valve with the corresponding second cam means are mounted in the rocker arm which actuates the corresponding valve in the first and second timed relations to the rotation of the crankshaft.
 35. The apparatus according to claim 26, wherein the first and second cam means for each valve capable of being actuated in two timed relations to the rotation of the crankshaft include a first profile and a second profile formed on a single cam, the first and second profiles being circumferentially spaced from each other.
 36. Apparatus for varying the timing of at least one of the valves of an internal combustion engine having a crankshaft and at least one cylinder associated with the valves, a piston reciprocable in each cylinder and connected to the crankshaft for rotation thereof, first cam means for actuating the valves in a first timed relation to the rotation of the crankshaft, second cam means for actuating at least one of the valves in a second timed relation to the rotation of the crankshaft, and a plurality of valve gear trains coupling the valves to the corresponding first and second cam means, comprising means forming a hydraulic chamber having an inlet port and adapted to receive pressurized fluid through the inlet port, a piston reciprocally disposed in the chamber, the hydraulic chamber forming means and the piston being a portion of each valve gear train coupling a valve with the corresponding second cam means, check valve means for trapping the pressurized hydraulic fluid in the chamber and preventing the trapped fluid from exiting the chamber through the inlet port, means for biasing the check valve means to seal the inlet port to prevent hydraulic fluid in the chamber from exiting therethrough, and control means for selectively disabling the check valve means and preventing hydraulic fluid in the chamber from being trapped therein, whereby when the check valve means is disabled, the piston is able to reciprocate in the chamber, the corresponding second cam means are rendered ineffective, and the corresponding valve is actuated in the first timed relation to the rotation of the crankshaft. 